Centrifugal mercury switch



July 11, 1933. G e L EN 1,917,581

CENTRIFUGAL MERGUBY SWITCH Filed Jan. 25, 1952 2 Sheets-Sheet 1 flaw/ye 67. 627/2.

July 11, 1933. GILLEN 1,917,581

CENTRIFUGAL MERCURY SWITCH Filed Jan. 25, 1952 Z SheetS-Sheet 2 Z .VE-sf 242-4;

Patented July 11, 1933 UNITED STATES PATENT OFFICE- GEORGE A. GILLEN, OF BRONX, NEW YORK, ASSIGNOR 'I'O CAKES PRODUCTS CORIPO- RATION, OF NORTH CHICAGO, ILLINOIS, A CORPORATION OF MICHIGAN CENTRIFUGAL MERCURY SWITCH Application filed January 25, 1932. Serial No. 588,728.

This invention relates to a centrifugal mercury switch which is adapted for general use but which is designed particularly for use in a hydro-carbon engine automatic starting system to be governed by the speed of the engine to control the opening and closure of the electrical circuit forthe engine starting motor.

An important object of the invention is to produce a simple, compact, efiicient and economically manufactured switch structure or unit which may be readily connected to receive its driving power either directly or indirectly from the engine so that its operation will be in accordance with the speed of rotation of the engine while the engine is being started or is running.

A further object of the invention is to adapt the mercury switch, when used for controlling the starting circuit of an engine, to respond rapidly to cause opening of the starting circuit immediately after starting of the engine by the starting motor, and to delay reclosure of the starting circuit until the engine has come to rest after some failure to keep up its running condition.

The above enumerated and other features of the invention are shown incorporated inthe structure disclosed on the drawings, in which drawings Figure 1 is a side elevation of the switch structure and a generator on which the switch is mounted for common drive therewith, the enclosing shell of the switch structure being in diametral section;

Figure 2 is an enlarged diametral section of the switch structure;

Figure 3 is a plan view of a sheet metal stamping on which is formed a supporting frame for the switch element;

Figure 4 is a section on plane IVIV of Figure 1;

Figure 5 is a section of the switch head on plane VV of Figure 2;

Figure 6 diagrammatically discloses a starting system for an engine and the switch unit included therein. 7 i

The switch structure shown comprises a cylindrical cup 10 of insulating material such as the material known commercially as bakelite. The cup has a cover 11 intimately secured thereto by a suitable joint 12 which will prevent leakage from the cup of the mercury 13. A transverse wall or plate 14 is mounted within the cup and divides it into an inner chamber 15 and an outerchamber 16, the inner chamber being preferably concave and the outer chamber being cylindrical and of larger diameter and volume than the chamber 15. The partition Wall 14 has a circumferential row of restricted ports 17 therethrough located just within the rim of the inner chamber 15.

Extending through the bottom wall of the cup 10 at the axis thereof is a contact block 18 whose inner end is exposed to the mercury within the cup and whose outer end is adapted for engagement by a contact member 19. Surrounding the inner contact block 18 1s a contact ring 20 concentric therewith and extending through the cup bottom for exposure at its inner edge to the mercury and for engagement at its outer end by a contact member 21.

The quantity of mercury in the cup is such that when the cup is at rest the level of the mercury will be such that the inner contact 18 is well covered, the mercury then forming a means for electrically connecting the inner contact with the outer contact ring 20. During slow rotation of the cup, as for example during the starting of an engine by the starting motor, the mercury will substantially retain its level in the cup and keep the contacts 18 and 20 electrically connected. However, when the speed issuddenly and rapidly increased, as for example after starting of the engine and running thereof, the

action of centrifugal force on the mercury Will cause radial outward displacement thereof, the centrifugal action causing the mercury within the inner chamber 15 to be crowded outwardly along the inclined bottom of the chamber and through ports 17 into the outer chamber 16 and as the mercury is thus receded from the inner contact 18 this contact will no longer have electrical connection with the contact ring 20, the greater part of the mercury being Within the outer chamher 16 into which it is crowded by the centrifugal action.

When the speed of rotation is suddenly decreased and the mercury becomes released from violent centrifugal action, the mercury tends to resume its normal level in the cup 10, but to do this, the mercury must flow back into the inner chamber 15 through the restricted ports 17 and the return of the mercury to normal level in the inner chamber is thus retarded and delayed. Where the switch is used With a starting system for an engine, this drag or delay of mercury flow prevents reclosure of the engine starting motor circuit until the engine has come substantially to rest. The switch thus operates automatically to rapidly close the circuit when the engine is started to run, but reclosure of the circuit upon failure of running condition for the engine is delayed until the engine has come to rest.

In the structure shown, the cover 11 of the switch cup has a stud 22 extending axially therefrom to be received in the end of a drive shaft 23 and rigidly secured thereto as by means of a pin 24. The frame shown for supporting the shaft 23 omprises a cylindrical head 25 having the flange 26 extending radially from its inner edge, and a number of equally spaced legs 27 extending in axial direction from the periphery of the flange. The head 25 has the opening 28 through its outer wall through which the shaft 23 extends to support at its outer end a belt pulley '29. A ball bearing structure 30 within the head 25 journals the shaft and a packing washer structure 31 is interposed between the ball bearing and the shaft to seal against the entrance of dirt through the opening 28. The inner end of the shaft which receives the stud 22 on the mercury cup is journalled in a cross wall 32 extending between and secured to the legs 27.

An enclosing casing or shell 33 which may be cylindrical and of sheet metal is slipped over the wall 32 and the legs 27 and seats against the flange 26, a screw 34 detachably locking the shell in closing position, the shell when secured being'concentric with the shaft 23 and the mercury switch cup. The bottom wall of the shell 33 supports terminal bolts or screws 35 and 36 connected respectively with the contact members 19 and 21 which member such as a belt driven directly or indirectly by the engine of the vehicle. As shown in Figure 1, the switch structure is supported on a generator G which is driven from the engine by means of a belt 38 engaging the driving pulley 39 for the generator. The switch structure is mounted on the generator so that its pulley 29 is also engaged by the belt 38, the rotation of the mercury switch element then depending upon the rotation of the engine. As shown, a supporting arm 40 extending from the flange 26 of the switch supporting frame is secure to the engine generator frame by means of screws 41. The main supporting frame for the switch structure may be formed from a stamping as disclosed in Figure 3, the body 42 of the stamping being de flected in suitable dies to form the head 25 and the flange 26, the equally spaced radially extending part 27 on the body 42 being then deflected to form the axially extending legs 27 which support the bearing wall 32. The extension 40 on the stamping terminates in a substantially semi-circular end 43 which forms a supporting base for the completed frame for engaging the ends of the frame of the generator, the elongated slots 45 receiving the screws 41 so that adjustment may be made of the switch structure relative to the generator in order to apply the driving pulley 29 with the proper friction against the belt 38.

Figure 6 diagrammatically shows a starting system for an automotive engine. The system includes an electromagnet switch S comprising a movable switch member 47 pivoted for oscillating movement by a suitable pivoting support 48 and carrying a switch blade 49 having the deflected contact ends 50 and 51, for engagement with the terminal structures 52 and 53. The blade 49 may be slidable longitudinally in the slot 47 so that the blade may accurately engage its ends with the terminals.

Means such as a spring 55 is provided tending to rotate the block 47 to disengage the switch blade from the terminals 52 and 53, and an electromagnet is provided for moving the switch to engage the terminals. The electromagnet comprises a suitable energizing winding 56 and an armature or core 57 connected by a link 58 with the switch block 47 at one side of its pivot support so that when the winding receives current flow the armature will be attracted and the switch block rotated to engage the switch blade with the terminals.

The switch terminal 52 is connected by a conductor 59 with one terminal of the battery 60 whose other terminal is connected with ground as indicated while the conductor 61 extending from the terminal 53 is connected with ground and includes the engine starting motor diagrammatically indicated at 62. Thus when the electromagnet closes the switch the starting motor will be connected in circuit to start the engine.

The winding 56 of theelectromagnet is included in the circuit 63 which is grounded at one end and at its other end is adapted for connection with the battery 60 through a switch I which may be the ignition controlling switch for the engine. The ignition switch comprises a V-shaped switch lever 64 and the contacts 65, 66 and 67, the contacts 67 and 68 being connected with one side of the primary winding 69 for an ignition coil whose other terminal is grounded. When the switch lever 64 is moved to engage the contacts 65 and 67 the ignition coil will be connected in circuit and the circuit 63 for the electromagnet winding will be closed at one point. If the switch blade engages only the contact 68 then the ignition coil will be connected with the battery but not the electromagnet circuit.

The circuit 63 also includes the contact nor switch structure. When the engine is at rest with the mercury in the mercury switch at normal level the contacts 18 and 20 engaged by the brushes 19 and 21 are electrically connected by the mercury and then when the ignition switch is closed the energizing circuit 63 is closed and the electromagnet is energized and the switch block 417 is rotated to engage the switch blade with the terminals 52 and 53 to cause closure of the starting motor circuit whereupon the motor operates to rotate the engine to start the same. During comparatively very slow rotation of the engine by the starting motor, the mercury level in the mercury switch will not be materially changed and therefore the electromagnet energizing circuit remains closed during operation of the starting motor and until the engine has been started and its speed has materially increased. Then centrifugal action on the mercury will displace it radially outwardly and away from the inner contact 18 and the energizing circuit 53 is automatically opened and the starting motor is connected. So long as the engine is running the mercury switch will keep the energizing circuit open. Should anything happen to the engine or control therefor so that the engine cannot run, it will immediately lose its running speed and eventually come to a stop. As soon as the engine loses its running speed, the centrifugal force no longer controls the mercury and the mercury will tend to flow back to assume its normal level. As has already been explained, such flow of the mercury back into the inner chamber 15 for engaging with the contact 18 is retarded or delayed by the restop or so close to full stop that there will be no danger of injury to the starting motor when it is again coupled to the engine when the energizing circuit for the switch closing electromagnet is reclosed by the mercury. As soon as the energizing circuit is reclosed the starting motor is again connected in circuit and the engine will be restarted and then centrifugal force substantially immediately displaces the mercury for disconnection of the contacts 18 and 20 and reopening of the energizing circuit.

If the driver does not desire to use the automatic starting circuit the ignition switch blade 61 is swung to engage only with the contact 68, the ignition circuit being then connected for service and the engine can then be started by cranking or otherwise.

l have shown and described a practical and efficient embodiment of the features of my invention, but I do not desire to be limited to the exact details as shown, as changes and modifications may be made in the construction, arrangement and operation without departing from the scope of the invention as defined by the appended claims.

1 claim as follows:

1. A centrifugal switch comprising a container rotatable on a horizontal axis, a vertical partition dividing said container into an inner concave chamber and an outer cylindrical chamber of greater radial extent than said inner chamber, said chambers being concentric with the axis of rotation of the container, a contact projecting into said inner chamber at the apex thereof, restricted passageways through said partition adjacent to the outer end of said inner chamber, electrically conductive fluid in said chamber normally at a level to engage said contact when the fluid is not subjected to centrifugal action, the inclined wall of said inner chamber causing the fluid to be crowded from the inner chamber through said restricted passageways and to the outer chamber when said fluid is subjected to centrifugal action by the rotation of said container whereby the fluid will be withdrawn from said contact, said restricted passageways retarding the return of the fluid to said inner chamber and in engagement with said contact after release of said fluid from centrifugal action.

2. A centrifugal switch comprising a con,- tainer rotatable on a horizontal axis, a vertical partition dividing said container into a concave chamber and a cylindrical cham'- ber of greater radial extent than said concave chamber, said chambers being concentric with the axis of rotation of said container, an inner contact on said container at the apex of said concave chamber and an annular contact surrounding said inner contact, said contacts communicating with the interior of said concave chamber, there being restricted by the rotation of said container whereby the fluid will be withdrawn from said inner contact, said restricted passageways retarding the return of fluid to said concave chamber after release of said fluid from centrifugal action whereby reconnection of said contacts is retarded.

In testimony whereof I have hereunto subscribed my name at Chicago, Cook County,

Illinois.

GEORGE A. GILLEN. 

